This application relates to a poppet valve wherein a flow cross-sectional area varies linearly with movement of the valve.
Valves are utilized in any number of applications. In one particular application, valves are utilized as an expansion device in a refrigerant cycle, such as a vapor cycle. Essentially, a fluid is compressed, then passed through a first heat exchanger. Fluid downstream of this heat exchanger passes through an expansion device at which the fluid flow is restricted such that the fluid expands across the restriction. This expanded fluid then passes through another heat exchanger before returning to the compressor.
Some expansion device valves have used poppet valves having a conical valve pin movable relative to a valve seat. As the conical valve pin moves, a flow cross-sectional area changes. The flow cross-sectional area is defined by the valve pin outer diameter, and a valve seat orifice inner diameter. As a conical valve pin strokes, the inner radius varies linearly. However, because the area of a circle is a function of the radius squared, the area does not vary linearly with linear valve poppet movement.
Controls for the position of a conical pin must be programmed to achieve a desired flow cross-sectional area with the ability to calculate the constantly varying movement. This requires precise, complex positioning of the valve pin.